1. Field of the Invention
The present invention generally relates to a method and apparatus, and more particularly to a method and apparatus for image processing which is capable of performing a density adjustment with respect to an output data signal for optical writing in which gray-scale is performed by at least one of plural methods including a manipulation of a plurality of dots, a density adjustment on a single dot, and a size adjustment on a single dot.
2. Discussion of the Background
In an image forming apparatus, density of a pixel is generally adjusted with a manipulation of a plurality of dots arranged in a form of matrix, a single-dot-based density adjustment, or a single-dot-based size adjustment. Various image density adjusting methods using multiple-value dithering have been developed. One example is Japanese Laid-Open Patent Application No. 3-80768 (1991). In this example, density adjustment with dithering is first performed with respect to multiple-value input image data. Then, multiple-value dithering is performed on the adjusted input multiple-value image data. Finally, density correction according to a printer output characteristic is performed on the resultant multiple-value dither data. With this method, density adjustment on multiple-value input image data can suitably be made to a variety of printer characteristics.
However, the above-described method cannot reproduce an optimal dot in accordance with conditions of neighboring dot positions. That is, the above method will make an inferior reproduction with respect particularly to a highlight or line portion. Further, it performs the multiple-value dithering using a single gamma correction table. Therefore, the above method cannot produce an output data signal for image writing in which gray-scale is performed for various different density adjustment operations based on, for example, a manipulation of a plurality of dots, a density adjustment on a single dot, and a size adjustment on a single dot.